Zombie AI - experimental rules

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Zombie AI - experimental rules

Postby Dr StrangeBrik » Thu Jul 15, 2010 5:03 pm

Advance warning for ADD folk. If you have a natural aversion to the "Wall o Text" phenomenon, you may not want (or be able) to read further...

Everbody else, please read on, and offer your comments, suggestions etc.

Zombie rules:
These are my experimental rules for zombie behaviour (I’m still playtesting). They should allow you opportunity to create scenarios where you have groups of player-controlled minifigs trying to negotiate an area that is infested with NPC zombies that act in a fairly natural zombie-esque manner... mmm braiiins....

Hopefully these rules should provide a reasonably robust zombie AI, and allow you to have numbers of the shambling undead autonomously wandering about your games, forming clusters and seeking out sources of fresh meat... The idea was to provide a fairly accurate simulation of zombie behaviour (based on all those George Romero films I have watched recently) without a mind-numbing amount of dice rolling completely bogging everything down. The more zombies you have, the more likely they are to form clusters, which quickly brings down the amount of dice rolls needed for the simulation. The rules look better in a flow chart (I’m working on one).

Stats:
Move: d6” (usually random direction)
Armour: 5
Skill: 1d6 -1

Zombies are generally in one of four states:
1. Standing still (loitering)
2. Wandering aimlessly
3. Purposefully focussed (requires something gaining its attention)
4. feeding/attacking (requires contact with suitable prey)

Zombies are slow (I’m thinking classic Romero style zombies here)
Move = d6”

Zombies are single minded of purpose
Not being known for original thought, zombies often follow whatever behaviour they were previously doing. A lot of the time, what they do next, will be dependant on what they did last turn.

To aid in keeping track of what individual zombies were previously up to, I suggest the simple expedient of using the zombie minifig’s arms to indicate what they did last turn:

A zombie standing still - both arms down by sides
A zombie wandering aimlessly - one arm raised in front.
A purposeful zombie - both arms raised out in front (assuming of course that does have two arms)

Each time the zombie’s turn comes up, roll a d6 to determine what it will do.

Starting roll - first zombie turn (d6):
- 1-3 Stand in one spot (arms down)
- 4-6 wander aimlessly (one arm forward) d6” in random direction

Subsequent turns:

If stood still last turn:
- 1-4 Remain standing in one spot (arms down)
- 5-6 wander aimlessly (one arm forward) d6” in random direction
(Once they are stopped, zombies tend to stay put - unless something takes their fancy...)

If wandered last turn:
- 1-2 Stop
- 2-4 - Continue in same direction as before
- 5-6 - pick a new random direction to wander

Zombies don’t handle obstacles well.
Zombies aren’t good climbers, so they cannot climb trees or ladders (stairs are OK though, and they will climb through un-barricaded windows just fine if they present a large enough opening). Other objects greater than 2 bloks high count as impassable obstacles. If a zombie encounters an impassable obstacle, roll 1d6. 1-2 = the zombie stops, 3-4 = it moves left, 5-6 = it moves right (if right or left is blocked, it will automatically move the other direction - to save another die roll).

A purposeful (see below) zombie (or group - see later) that encounters a fence that lies between it and its intended feast of tasty flesh, once stopped (ie, not trying to move left or right), will attempt to attack the fence on subsequent turns on a roll of 5-6 (and continue to do so from then on). The zombie(s) do need to be able to have line of sight to their intended target in order to continue attacking the intervening obstacle (otherwise they simply stop and stand there groaning). Multiple zombie attacks on walls/fences are cumulative and may count as grinding.

Zombies will move toward the living, but may not always notice them.
Zombies are unaware of people staying still and quiet beyond 6” distance. If any zombie gets closer than this to someone, they will attract the zombie’s attention.

Zombies are attracted to meat and noise.

Any fresh meat (bait?), or gunfire, radio chatter, cellphone rings, sprinting, shouting, vehicle engines within 12” will attract a zombie’s attention.

Even if further away than 12”, hitting a zombie with gunfire (assuming it survives the experience) will cause it to move in the direction of the attack.

If something attracts a zombie’s attention, it is now “purposeful” - bring both arms forward (if it has two arms of course). It will move d6” towards the target that turn. Every turn thereafter, it will continue to move toward the target on a d6 roll of 2-6 (on a 1, it will lose interest and make a starting roll to determine if it will remain stationary or wander aimlessly) If the target is still within 6” after the zombie’s movement ends, it will attract the zombie’s attention NEXT turn (assuming that the target is too lazy to be bothered to move away)..

Distracting purposeful zombies.
Once a zombie is purposeful, it will only be distracted by another source of noise if it is louder than the original target (or the original target stops making noise & moving - shooting at it only makes it more interested). Such distraction only works on a d6 roll of 5 or 6.

If a zombie makes contact with the target, it will attack (even if it wasn’t purposeful for some reason or other).
Once attacking, it will only be distracted if the target is dead and eaten (takes one full turn after killing the target), or something else attacks it directly.

Zombies only attack with hands & teeth (again with the biting already).
A single melee attack (as if with random object), Use = 3, Damage 1d6-1
Zombies do not parry, but may make a single counterattack.
Individually fairly weak, their strength is in numbers and sheer tenacity and resilience (“head-shot’s the only real stopper Barry”).

Movement - clusters of zombies


Any two zombies (or two groups of zombies) that move to within 2” of each other may combine to form a bigger group at the end of their movement phase (d6 roll of 2+ if the new arrival(s) fail to join the group, then move them so that they are slightly more than 2” away to avoid confusion). Once in a group all members will remain within 2” coherency of at least one other member of the group.

Groups of zombies tend to move together (zombies are insecure and like misery, prefer company).
In a given situation, you only make one roll for the whole group to determine what they do. They move and respond to their environment as one unit, as though you were dealing with a single zombie (just much wider), with the following differences:

• Distance at which zombies will notice you is measured from the outermost zombies in the group.
• Clustered zombies may combine attacks (but no more that 3 on one as per core rules).
• A group of zombies is less easy to block with obstacles. Unless an obstacle is large and wide enough to impede the progress of the whole group, it will simply “flow” through gaps and around obstacles.
• Purposeful groups of zombies are only distracted on a roll of 6, and are not able to be distracted from melee until their targets are all dead and thoroughly chewed on (one full turn after the targets are killed, basically the group spends their action for their next turn gnawing on the fresh corpses).

The attention of a purposeful cluster is focussed as a whole. All of the group will move toward the same target. If two targets present, the group will move toward the closest (or the loudest - fudge a rule for which is loudest if need be). If targets are about the same distance away, the group will either move toward both (if they are close to each other), spreading to reach, or the group will split into roughly equal clumps (if the targets are widely separated). If there are more than two competing sources of stimuli, the zombie cluster, unable to count to more than two, will simply pick one source at random and move toward that one. This makes groups of zombies fairly easy but not completely predictable, to herd.

Zombification
Any minifigs that are killed by zombies will themselves be resurrected as zombies in the following zombie turn. This can be prevented by immolating (or gibbing - through excessive amounts of damage) the corpse. Dissolving in acid or molten lava also work quite well...

Naturally, of former team-mates of the newly formed zombies are within 6”of them when they make their debut, they will immediately become purposeful and move to secure a free meal as per normal zombie behaviour.

Optional: Infection.
Any minifig that is successfully wounded by a zombie, but not killed (eg. Their armour absorbed the damage). May be infected and will zombify upon its eventual death on a d6 roll of 1-2 (you will need to have some way of marking potential infectees so you won’t forget who needs to roll when they die). It does add another level of complexity to an already fairly busy system, but it does create amusing situations if later in the battle, casualties start getting up and chowing down on their former mates...
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Postby RunsWithLegos » Thu Jul 15, 2010 5:28 pm

this is perfect. i think i am going to implement these rules in ATL
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Postby Ross_Varn » Thu Jul 15, 2010 6:22 pm

Holy shit. I'm printing this.

Thanks, Doc. Excellent supplement.
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Postby Elmagnifico » Thu Jul 15, 2010 7:34 pm

I like these, just a quick streamlining note:

If something attracts a zombie’s attention, it is now “purposeful” - bring both arms forward (if it has two arms of course). It will move d6” towards the target that turn. Every turn thereafter, it will continue to move toward the target on a d6 roll of 2-6 (on a 1, it will lose interest and make a starting roll to determine if it will remain stationary or wander aimlessly) If the target is still within 6” after the zombie’s movement ends, it will attract the zombie’s attention NEXT turn (assuming that the target is too lazy to be bothered to move away)..


Perhaps this could also be the Zombie's movement roll? Just so we have one less die to roll.
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Postby Dr StrangeBrik » Thu Jul 15, 2010 8:18 pm

Good idea. I'm all for streamlining the number of dice rolls. it's a balancing act of trying to get a reasonable simulation, and keeping it manageable in terms of dice usage.

If anyone tries these rules out, be sure to let us know how they function in gameplay (my own playtesting has been limited to smaller numbers of zombies so far).
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